Added function to update of custom_gcode_per_print_z in Model from configuration

considering "colorprint_heights" option.

Changed thumb_up/down icons to better preview (feedback from #3256)

Commented some uncertain code

resources/icons/thumb_down.svg

@@ -4,7 +4,7 @@
 	 viewBox="0 0 16 16" enable-background="new 0 0 16 16" xml:space="preserve">
 <g id="hex_x5F_plus">
 	<g>
-		<polygon fill="#ED6B21" points="2,8 2,11 8,15 14,11 14,8 "/>
+		<polygon fill="#ED6B21" points="1,8 1,11 8,16 15,11 15,8 " style="stroke:white;stroke-width:1"/>
 	</g>
 </g>
 </svg>

resources/icons/thumb_up.svg

@@ -4,7 +4,7 @@
 	 viewBox="0 0 16 16" enable-background="new 0 0 16 16" xml:space="preserve">
 <g id="hex_x5F_plus">
 	<g>
-		<polygon fill="#ED6B21" points="8,1 2,5 2,7 2,8 14,8 14,7 14,5 		"/>
+		<polygon fill="#ED6B21" points="8,0 1,5 1,7 1,8 15,8 15,7 15,5" style="stroke:white;stroke-width:1"/>
 	</g>
 </g>
 </svg>